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Old 10-10-2011, 07:38   #1
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Heating with Waste Heat from the Engine

Some other threads have got me thinking again about trying to get some benefit from my engine's waste heat this winter.

I have an Eberspaecher (Espar) Hydronic 10 diesel-fired furnace which circulates hot water to three fan coils and to a loop in my domestic hot water calorifier.

I do have an engine waste heat loop in my calorifier, too. Engine coolant from the engine's fresh water cooling circuit is -- theoretically -- circulated through a separate loop in the calorifier. In fact, it does not work.


I am guessing that the simplest best way to get engine waste heat into my heating system is with a water-to-water heat exchanger. If I circulate the Espar's coolant through a heat exchanger heated by the engine's fresh water circuit, then all I have to do is switch on the Espar. The diesel-burning furnace will be throttled back automatically when it feels warmth in its coolant. And when the engine is not putting out enough heat to fulfill demand, the furnace will throttle up.

Right?

If so, then there is the question of system architecture. I see two main variants:

1. Plumb in the heat exchange into the return line returning engine coolant from the calorifier. Then plumb the other side of the heat exchanger into the Eber's loop -- into the return side returning coolant to the furnace.

Question: Does the Eber's calorifier loop have the same flow as the rest of the system? Does it have a separate pump? If not, then maybe better splice it into a fan coil return line.

2. Get rid of the engine coolant loop in the calorifier altogether. Make a short loop through the water-to-water heat exchanger and then plumb the Eber's calorifier loop through the other side.

Advantage: Short, more efficient circulation of engine coolant -- flow will be greater and temperature higher.

Disadvantage: No heat in the calorifier unless the Eber is switched on (unless I put in a separate pump, or rewire the Eber's controls).


Comments?
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Old 10-10-2011, 08:07   #2
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Re: Heating with Waste Heat from the Engine

be careful about using the engines cooling system to transfer heat as the circulation pump is not designed as a lift pump.

a second coolant reservior at the highest point of the loop may also be needed to prevent airlocks if the heat exchanger/calorifier is higher than that of the engine reservior.

best results would be achieved buy installing a direct system similar to a truck/car heater, ie blown air through a radiator.
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Old 10-10-2011, 08:12   #3
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Re: Heating with Waste Heat from the Engine

Thanks.

Variant 3: Install TWO heat exchangers. One feeds the calorifier. The other feeds the Eber. Expensive, but ought to be very good.


I presume that installing an electric boost pump in the engine's fresh water circuit is a no-no?
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Old 10-10-2011, 08:13   #4
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Re: Heating with Waste Heat from the Engine

We have a Heatercraft forced air heater plumbed into our engine cooling system that works very well and was easily installed.

FWIW...
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Old 10-10-2011, 08:15   #5
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Re: Heating with Waste Heat from the Engine

Translation to North American: "Calorifier" is "hot water heater".

I would be concerned about differing pressures and the possibility of backflow in such a system, but I don't think it's inherently faulty. I do not know how much useful, extractable heat is going to be left in the return line to the heat exchanger after a trip to the calorifier.

I have one of those hot water heaters that runs either on an AC circuit hooked into an immersion element, much like a six-gallon kettle, or via a heat-exchanger circuit. Both work properly, but I've realized that my needs for volumes of hot air are transitory, whereas my need for a warm, dry boat is more constant. At dock, we run a Mermaid Marine Air 12,000 BTU heat pump unit, but at sea I would prefer an Espar or Wallas or Webasto style diesel heater. My challenge is figuring out how to run both units through the same vent system without melting something, as I would prefer not to have side by side conduits.
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Old 10-10-2011, 08:41   #6
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Re: Heating with Waste Heat from the Engine

im in the process of building a heating system so have similar issues.

ie i have a drip fed backboiler and a mikumi hydronic closed loop diesel heater designed for radiators ,this requires a closed loop of piping around the boat,NOT something i would want to tee the engine cooling system into.

with your existing system i assume it is a ducted blown air system,why not tee in to that by installing a dedicated radiator type ,air blown heaterbox close to the engine?
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Old 10-10-2011, 09:22   #7
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Re: Heating with Waste Heat from the Engine

Quote:
Originally Posted by atoll View Post
im in the process of building a heating system so have similar issues.

ie i have a drip fed backboiler and a mikumi hydronic closed loop diesel heater designed for radiators ,this requires a closed loop of piping around the boat,NOT something i would want to tee the engine cooling system into.

with your existing system i assume it is a ducted blown air system,why not tee in to that by installing a dedicated radiator type ,air blown heaterbox close to the engine?
No it's not ducted blown air -- it's hydronic. So the 10kW Eber/Espar furnace (which lives in the lazarette) pumps heated water around the boat. There are three fan coils which turn the heat from this water into hot air, and one loop goes into the calorifier (hot water heater).

I would never connect the Eber's coolant loop with the engine's fresh water cooling -- recipe for disaster. I am considering putting in one or two water-to-water heat exchangers so that heat can be transferred from the engine fresh water circuit into the Eber heating circuit.

I don't know if the flow of engine fresh water coolant is enough to transfer enough heat 10 or 15 feet away. I think about mounting one or two heat exchangers quite close to the engine so the engine's fresh water coolant pump has less work to do, and flows better.

On the other hand, it would be dead simple to mount a heat exchanger right at the calorifier, because both loops are present right there (the calorifier has separate loops for engine fresh water, and for the Eber's heated water circuit). Maybe I'll try that first and see how it works.
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Old 10-10-2011, 10:02   #8
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Re: Heating with Waste Heat from the Engine

sounds like a plan,but i dont know how effcient a water to water heat exchanger is going to be.

a blown air unit situated close to the engine may be the cheapest and simplist option.

i picked up a new unit of ebay for a bus for 60! 650 new
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Old 10-10-2011, 10:17   #9
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Re: Heating with Waste Heat from the Engine

Kalori Zephyr 3D 24V - Kuranda

try these guys,heater matrix unit that can run direct off engine coolant circuit
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Old 10-10-2011, 10:22   #10
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Re: Heating with Waste Heat from the Engine

to some degree you already have a heat exchange system based on how you describe your plumbing. The engine fresh water circuit goes to your hot water heater. I assume there is no thermostat to shut this down so as long as your engine is making heat it is being transferred to the hot water heater.

The circuit from your hydronic heat also runs through the hot water heater and will be picking up heat as it passes through. This loop is thermostatically controlled so with throttle back as the temps come up and the engine heat will continue to be dumped into the system since it has no such control.

You can probably get some increased heat transfer with a dedicated heat exchanger but probably only a marginal improvement.

Btw, you can use a boost pump in the coolant circuit to your hot water heater. Helped a neighbor install one.
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Old 10-10-2011, 11:40   #11
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Re: Heating with Waste Heat from the Engine

Quote:
Originally Posted by svHyLyte View Post
We have a Heatercraft forced air heater plumbed into our engine cooling system that works very well and was easily installed.

FWIW...
I have the same unit laying out just about to install it in our catamaran, I hope it is as easy to install as you guy's say it is. This is our first step and getting a Hydronic disel system installed next year is our plans.
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Old 10-10-2011, 20:25   #12
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Re: Heating with Waste Heat from the Engine

Quote:
Originally Posted by svHyLyte View Post
We have a Heatercraft forced air heater plumbed into our engine cooling system that works very well and was easily installed.

FWIW...
+1

The Heatercraft heaters are great, work very well, and are easy to install. Hamilton Marine online has great pricing on them.

Also consider when doing your install, plumbing the furnace in such a way as it acts as a preheater for your engine. This is common on RV bus conversions in the North. They use a Webasto hydronic heater to heat the bus and also act as an engine preheat. Might be some useful information at their website:

Scholastic Heater



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Old 10-10-2011, 21:06   #13
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Re: Heating with Waste Heat from the Engine

Quote:
Originally Posted by Dockhead View Post
Question: Does the Eber's calorifier loop have the same flow as the rest of the system? Does it have a separate pump? If not, then maybe better splice it into a fan coil return line.
I don't know about Eber's colorifier, but I had a Webasto hydronic system on my previous boat where I installed a separate pump on a toggle so that I could run the system off the engine when motoring without having to run the furnace as well. Great for those all-night slogs through the fog when the wind is non-existent.

It was not only free heat, but it kept the engine just a tad cooler.
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Old 10-10-2011, 21:58   #14
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Re: Heating with Waste Heat from the Engine

Quote:
Originally Posted by Bash View Post
I don't know about Eber's colorifier, but I had a Webasto hydronic system on my previous boat where I installed a separate pump on a toggle so that I could run the system off the engine when motoring without having to run the furnace as well. Great for those all-night slogs through the fog when the wind is non-existent.

It was not only free heat, but it kept the engine just a tad cooler.
Great advice. I recently installed an OL-60 hydronic system with 9 fan heaters, an everhot, a dedicated defroster for the pilothouse windows, etc. etc. Think I'll have to look at adding a pump for that purpose as well. Free heat is good!
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Old 11-10-2011, 04:43   #15
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Re: Heating with Waste Heat from the Engine

Quote:
Originally Posted by andrewsc View Post
to some degree you already have a heat exchange system based on how you describe your plumbing. The engine fresh water circuit goes to your hot water heater. I assume there is no thermostat to shut this down so as long as your engine is making heat it is being transferred to the hot water heater.

The circuit from your hydronic heat also runs through the hot water heater and will be picking up heat as it passes through. This loop is thermostatically controlled so with throttle back as the temps come up and the engine heat will continue to be dumped into the system since it has no such control.

You can probably get some increased heat transfer with a dedicated heat exchanger but probably only a marginal improvement.

Btw, you can use a boost pump in the coolant circuit to your hot water heater. Helped a neighbor install one.
Thanks. I thought about this. My engine fresh water circuit has not been heating my hot water -- it is apparently air locked. If I clear the air lock, I think that there will be some heat transfer from the engine to the Espar circuit.

But I don't think that two loops intended to make 50 liters of hot water is going to transfer enough heat to heat the boat. I think a real heat exchanger would be the thing.

The installation would be a snap if I do it right next to the calorifier (which itself is well accessible under my salon sole). A boost pump would remove concerns that I wouldn't get enough coolant circulating there.

I am intrigued by your comment -- you helped a neighbor install a boost pump in his engine freshwater cooling circuit? Works ok? Does not interfere with the engine's regular water pump?
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